objtool,x86: Simplify register decode

Since the CFI_reg number now matches the instruction encoding order do
away with the op_to_cfi_reg[] and use direct assignment.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lkml.kernel.org/r/20210211173627.362004522@infradead.org

diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index 47b9acf..5ce7dc4 100644 (file)
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -17,17 +17,6 @@
 #include <objtool/arch.h>
 #include <objtool/warn.h>
 
-static unsigned char op_to_cfi_reg[][2] = {
-       {CFI_AX, CFI_R8},
-       {CFI_CX, CFI_R9},
-       {CFI_DX, CFI_R10},
-       {CFI_BX, CFI_R11},
-       {CFI_SP, CFI_R12},
-       {CFI_BP, CFI_R13},
-       {CFI_SI, CFI_R14},
-       {CFI_DI, CFI_R15},
-};
-
 static int is_x86_64(const struct elf *elf)
 {
        switch (elf->ehdr.e_machine) {
@@ -94,7 +83,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
        unsigned char op1, op2,
                      rex = 0, rex_b = 0, rex_r = 0, rex_w = 0, rex_x = 0,
                      modrm = 0, modrm_mod = 0, modrm_rm = 0, modrm_reg = 0,
-                     sib = 0;
+                     sib = 0 /* , sib_scale = 0, sib_index = 0, sib_base = 0 */;
        struct stack_op *op = NULL;
        struct symbol *sym;
 
@@ -130,23 +119,29 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
        if (insn.modrm.nbytes) {
                modrm = insn.modrm.bytes[0];
                modrm_mod = X86_MODRM_MOD(modrm);
-               modrm_reg = X86_MODRM_REG(modrm);
-               modrm_rm = X86_MODRM_RM(modrm);
+               modrm_reg = X86_MODRM_REG(modrm) + 8*rex_r;
+               modrm_rm  = X86_MODRM_RM(modrm)  + 8*rex_b;
        }
 
-       if (insn.sib.nbytes)
+       if (insn.sib.nbytes) {
                sib = insn.sib.bytes[0];
+               /*
+               sib_scale = X86_SIB_SCALE(sib);
+               sib_index = X86_SIB_INDEX(sib) + 8*rex_x;
+               sib_base  = X86_SIB_BASE(sib)  + 8*rex_b;
+                */
+       }
 
        switch (op1) {
 
        case 0x1:
        case 0x29:
-               if (rex_w && !rex_b && modrm_mod == 3 && modrm_rm == 4) {
+               if (rex_w && modrm_mod == 3 && modrm_rm == CFI_SP) {
 
                        /* add/sub reg, %rsp */
                        ADD_OP(op) {
                                op->src.type = OP_SRC_ADD;
-                               op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
+                               op->src.reg = modrm_reg;
                                op->dest.type = OP_DEST_REG;
                                op->dest.reg = CFI_SP;
                        }
@@ -158,7 +153,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
                /* push reg */
                ADD_OP(op) {
                        op->src.type = OP_SRC_REG;
-                       op->src.reg = op_to_cfi_reg[op1 & 0x7][rex_b];
+                       op->src.reg = (op1 & 0x7) + 8*rex_b;
                        op->dest.type = OP_DEST_PUSH;
                }
 
@@ -170,7 +165,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
                ADD_OP(op) {
                        op->src.type = OP_SRC_POP;
                        op->dest.type = OP_DEST_REG;
-                       op->dest.reg = op_to_cfi_reg[op1 & 0x7][rex_b];
+                       op->dest.reg = (op1 & 0x7) + 8*rex_b;
                }
 
                break;
@@ -223,7 +218,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
                break;
 
        case 0x89:
-               if (rex_w && !rex_r && modrm_reg == 4) {
+               if (rex_w && modrm_reg == CFI_SP) {
 
                        if (modrm_mod == 3) {
                                /* mov %rsp, reg */
@@ -231,17 +226,17 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
                                        op->src.type = OP_SRC_REG;
                                        op->src.reg = CFI_SP;
                                        op->dest.type = OP_DEST_REG;
-                                       op->dest.reg = op_to_cfi_reg[modrm_rm][rex_b];
+                                       op->dest.reg = modrm_rm;
                                }
                                break;
 
                        } else {
                                /* skip nontrivial SIB */
-                               if (modrm_rm == 4 && !(sib == 0x24 && rex_b == rex_x))
+                               if ((modrm_rm & 7) == 4 && !(sib == 0x24 && rex_b == rex_x))
                                        break;
 
                                /* skip RIP relative displacement */
-                               if (modrm_rm == 5 && modrm_mod == 0)
+                               if ((modrm_rm & 7) == 5 && modrm_mod == 0)
                                        break;
 
                                /* mov %rsp, disp(%reg) */
@@ -249,7 +244,7 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
                                        op->src.type = OP_SRC_REG;
                                        op->src.reg = CFI_SP;
                                        op->dest.type = OP_DEST_REG_INDIRECT;
-                                       op->dest.reg = op_to_cfi_reg[modrm_rm][rex_b];
+                                       op->dest.reg = modrm_rm;
                                        op->dest.offset = insn.displacement.value;
                                }
                                break;
@@ -258,12 +253,12 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
                        break;
                }
 
-               if (rex_w && !rex_b && modrm_mod == 3 && modrm_rm == 4) {
+               if (rex_w && modrm_mod == 3 && modrm_rm == CFI_SP) {
 
                        /* mov reg, %rsp */
                        ADD_OP(op) {
                                op->src.type = OP_SRC_REG;
-                               op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
+                               op->src.reg = modrm_reg;
                                op->dest.type = OP_DEST_REG;
                                op->dest.reg = CFI_SP;
                        }
@@ -272,13 +267,12 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
 
                /* fallthrough */
        case 0x88:
-               if (!rex_b &&
-                   (modrm_mod == 1 || modrm_mod == 2) && modrm_rm == 5) {
+               if ((modrm_mod == 1 || modrm_mod == 2) && modrm_rm == CFI_BP) {
 
                        /* mov reg, disp(%rbp) */
                        ADD_OP(op) {
                                op->src.type = OP_SRC_REG;
-                               op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
+                               op->src.reg = modrm_reg;
                                op->dest.type = OP_DEST_REG_INDIRECT;
                                op->dest.reg = CFI_BP;
                                op->dest.offset = insn.displacement.value;
@@ -286,12 +280,12 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
                        break;
                }
 
-               if (rex_w && !rex_b && modrm_rm == 4 && sib == 0x24) {
+               if (rex_w && modrm_rm == CFI_SP && sib == 0x24) {
 
                        /* mov reg, disp(%rsp) */
                        ADD_OP(op) {
                                op->src.type = OP_SRC_REG;
-                               op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
+                               op->src.reg = modrm_reg;
                                op->dest.type = OP_DEST_REG_INDIRECT;
                                op->dest.reg = CFI_SP;
                                op->dest.offset = insn.displacement.value;
@@ -302,7 +296,10 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
                break;
 
        case 0x8b:
-               if (rex_w && !rex_b && modrm_mod == 1 && modrm_rm == 5) {
+               if (!rex_w)
+                       break;
+
+               if (modrm_mod == 1 && modrm_rm == CFI_BP) {
 
                        /* mov disp(%rbp), reg */
                        ADD_OP(op) {
@@ -310,11 +307,12 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
                                op->src.reg = CFI_BP;
                                op->src.offset = insn.displacement.value;
                                op->dest.type = OP_DEST_REG;
-                               op->dest.reg = op_to_cfi_reg[modrm_reg][rex_r];
+                               op->dest.reg = modrm_reg;
                        }
+                       break;
+               }
 
-               } else if (rex_w && !rex_b && sib == 0x24 &&
-                          modrm_mod != 3 && modrm_rm == 4) {
+               if (modrm_mod != 3 && modrm_rm == CFI_SP && sib == 0x24) {
 
                        /* mov disp(%rsp), reg */
                        ADD_OP(op) {
@@ -322,8 +320,9 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
                                op->src.reg = CFI_SP;
                                op->src.offset = insn.displacement.value;
                                op->dest.type = OP_DEST_REG;
-                               op->dest.reg = op_to_cfi_reg[modrm_reg][rex_r];
+                               op->dest.reg = modrm_reg;
                        }
+                       break;
                }
 
                break;
@@ -339,11 +338,11 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
                        break;
 
                /* skip nontrivial SIB */
-               if (modrm_rm == 4 && !(sib == 0x24 && rex_b == rex_x))
+               if ((modrm_rm & 7) == 4 && !(sib == 0x24 && rex_b == rex_x))
                        break;
 
                /* skip RIP relative displacement */
-               if (modrm_rm == 5 && modrm_mod == 0)
+               if ((modrm_rm & 7) == 5 && modrm_mod == 0)
                        break;
 
                /* lea disp(%src), %dst */
@@ -356,9 +355,9 @@ int arch_decode_instruction(const struct elf *elf, const struct section *sec,
                                /* lea disp(%src), %dst */
                                op->src.type = OP_SRC_ADD;
                        }
-                       op->src.reg = op_to_cfi_reg[modrm_rm][rex_b];
+                       op->src.reg = modrm_rm;
                        op->dest.type = OP_DEST_REG;
-                       op->dest.reg = op_to_cfi_reg[modrm_reg][rex_r];
+                       op->dest.reg = modrm_reg;
                }
                break;